KR100813486B1 - A voltage supply circuit - Google Patents

Abstract

Provided is a voltage supply circuit which can quickly charge a capacitor constituting a time constant circuit when voltage supply is started, and easily adjust the amount of bias to be supplied to the transistor.

The voltage generation circuit is constituted by the time constant circuit 6 including the series circuit of the resistor R0 and the capacitor C0, and the series regulator type voltage generation circuit 7a provided on the input side thereof. Here, the first transistor Q1, the first transistor Q1, and the current mirror connected between the input terminal IN of the voltage supply circuit and the time constant circuit 6 are provided inside the voltage generation circuit 7a. Supply from the second transistor Q2 which operates, the third transistor Q3 which connected the main current path in parallel to the resistance R0 of the time constant circuit 6, and the 2nd transistor Q2. A bias circuit, specifically, a resistor R3, is provided for supplying a bias to the third transistor Q3 in accordance with the current. More preferably, the diode Q5 is connected in parallel with the resistor R0 of the time constant circuit 6.

Description

Voltage supply circuit {A VOLTAGE SUPPLY CIRCUIT}

1 is a circuit diagram of a voltage generation circuit and a time constant circuit according to the present invention.

2 is a block diagram showing a general arrangement inside an electronic device.

3 is a waveform diagram of a voltage signal output from a time constant circuit.

4 is a circuit diagram showing a charge promoting technique of a conventional voltage generation circuit and time constant circuit in the related art.

<Description of the symbols for the main parts of the drawings>

1: power 2: load device

3: power transistor 6: time constant circuit

7,7a: Voltage generating circuit AMP: Error amplifier

BG: Bandgap reference circuit C0: Capacitor constituting time constant circuit

IN: Input terminal of voltage generator circuit OUT: Output terminal of voltage generator circuit

Q1: transistor (first transistor) Q2: transistor (second transistor)

Q3: transistor (third transistor) Q5: transistor (diode)

R0: Resistor constituting the time constant circuit R3: Resistor (bias circuit)

V _D : Supply voltage from power supply V _R1 : Output voltage of voltage generating circuit

V _R2 : Output voltage of time constant circuit V _S : Supply voltage to load device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage generating circuit for supplying a predetermined voltage through an RC time constant circuit or a filter circuit, and by rapidly charging a capacitor installed in the time constant circuit, the startup operation of the entire apparatus in which they are installed at high speed is achieved. It relates to a technique for making it possible.

A general electronic device is established as an assembly of various device parts such as a signal processing device, a display device, and a driving device. If another device is started or stopped while some devices are in an operating state, a situation may arise in which a power supply voltage fluctuates or a noise that may cause a malfunction may enter the device during operation. For this reason, countermeasures such as providing a voltage stabilization circuit individually on the input side of each device, or in particular, providing an RC time constant circuit (also referred to as a filter and an integrating circuit) in a circuit location where voltage stabilization is required are required.

2 shows an example of the positional relationship between a power supply, a load device, a stabilization circuit, and a filter in an electronic device.

In Fig. 2, the high potential terminal of the power supply 1 is connected to one end of the load device 2 via the main current path of the Pch-MOS type power transistor 3, and the low potential terminal of the power supply 1 and The other end of the load device 2 is all connected to the ground. The gate of the power transistor 3 is connected to the ground via the main current path of the transistor 4, and the gate of the transistor 4 is connected to the signal output terminal of the error amplifier 5.

The inverting input terminal (-) of the error amplifier 5 is connected to the common connection point of the power transistor 3 and the load device 2, and the non-inverting input terminal (+) of the error amplifier 5 is the time constant circuit 6 )

Here, the time constant circuit 6 is composed of a series circuit of the resistor R0 and the capacitor C0, and one end of each of the resistor R0 and the capacitor C0 is a non-inverting input terminal of the error amplifier 5 ( Common connection to +). The other end of the capacitor C0 is connected to ground, and the other end of the resistor R0 is connected to the output terminal OUT of the voltage generating circuit 7. The input terminal IN of the voltage generating circuit 7 is connected to the high potential terminal of the power source 1.

In Fig. 2, the power transistor 3, the transistor 4, the error amplifier 5, the time constant circuit 6, and the voltage generator 7 constitute a voltage stabilizer circuit of a series regulator type. The voltage V _R2 supplied from the voltage generating circuit 7 through the time constant circuit 6 corresponds to the reference voltage of the series regulator. For this reason, even if the power supply voltage V _D of the power supply 1 fluctuates, if the fluctuation amount is smaller than the predetermined limit value and the fluctuation method is gentle, the supply voltage V _S supplied to the load device 2 is a voltage. The voltage V _R2 supplied from the generation circuit 7 through the time constant circuit 6 is stabilized at about the same magnitude.

On the other hand, when the fluctuation method of the power supply voltage V _D is extremely steep or when high frequency noise with a large fluctuation amount is superimposed, noise may occur in the output voltage V _R1 of the voltage generating circuit 7. There is this. When noise occurs in the output voltage V _R1 of the voltage generation circuit 7, the time constant circuit 6 functions as a filter for filtering out the noise, and thus the position of the non-inverting input terminal (+) of the error amplifier 5. The voltage V + in (= V _R2 ) becomes a voltage signal with little noise component. As a result, even if large noise is superimposed on the power supply voltage V _D , the supply voltage V _S maintains a stable value with little noise.

By the way, in order to reduce the noise component of the supply voltage (V _S) supplied to the load device 2, at least of the capacitance of the resistance value and the capacitor (C0) of the resistor (R0) constituting a time constant circuit (6) One may be made large enough to reduce the noise contained in the voltage V _R2 . However, when the resistance value of the resistor R0 and the capacitance of the capacitor C0 are increased, the error amplifier 5 is transferred from the time constant circuit 6 to the error amplifier 5 as shown by the curve a in FIG. 3 (= thick line). The "time from zero volt to the specified voltage" of the supplied voltage V _R2 becomes long. Then, when the start / stop of the load device 2 is performed by supplying / blocking the power supply voltage V _D from the power supply 1, the voltage supply from the power supply 1 is started and then the load device 2 is started. voltage (V _S) supplied to the discard delayed activation time also becomes longer load device (2) until reaching a predetermined value.

Therefore, when the supply of a low noise voltage is required for the load device 2 and the rapid start of the load device 2 is required, as shown in Fig. 4, the switch is turned on at the time of <1> start-up. A countermeasure was needed to connect S1 in parallel to the resistor R0, or to connect the switch S2, which is turned on at startup, between the power supply line Vcc and one end of the capacitor C0. . Incidentally, the countermeasure of <1> is mainly used when the voltage generating circuit 7 itself has sufficient current supply capability, and the countermeasure of <2> is used when the voltage generating circuit 7 itself does not have sufficient current supply capability. Used. In addition, a circuit for realizing the countermeasure of <2> in which one of the inventors of the present invention is involved in development is disclosed in Japanese Patent Laid-Open No. Hei 11-051981.

An important point in the countermeasures of <1> and <2> described above is that when the voltage between the terminals of the capacitor C0 is low, the switch S1 (or S2) is turned on, and after charging of the capacitor C0 is finished, Turns off the switch S1 (or S2). When a diode is connected in parallel with the resistor R0, the diode can be used as a switch S1 that is autonomously turned on and off depending on the current flowing through the resistor R0 and the voltage between the terminals of the capacitor C0. When the main current path of the transistor is connected between the power supply line Vcc and the capacitor C0, and the control terminal (= base) of the transistor is connected to the other end of the resistor R0, the transistor is connected to the resistor R0. It can be used as a switch S2 for autonomously turning on and off depending on the current flowing through the terminal and the voltage between the terminals of the capacitor C0.

However, when the diode as the switch S1 is connected in parallel with the resistor R0, the forward drop voltage generated in the diode becomes a factor of resisting the supply of current to the capacitor C0. For this reason, there is still room for improvement in terms of rapid charging of the capacitor C0.

On the other hand, when the transistor as the switch S2 is connected between the power supply line Vcc and the capacitor C0, and the base thereof is connected to a predetermined position of the resistor R0, the resistance value of the resistor R0 is mainly a time constant. It is determined according to the characteristics required for the circuit 6. For this reason, there is a problem that it is difficult to adjust the amount of bias to be supplied to the transistor at each time of turn on, turn off, and on state maintenance.

Therefore, an object of the present invention is to provide a voltage supply circuit which can quickly charge a capacitor constituting a time constant circuit when voltage supply is started, and easily adjust the amount of bias to be supplied to the transistor.

The present invention for solving the above problems is a voltage supply circuit for supplying a predetermined voltage to the functional circuit provided on the output side of the time constant circuit through a time constant circuit including a resistor and a capacitor, the voltage and current A first transistor provided between the input terminal and the time constant circuit so as to supply a voltage, and a control terminal thereof is commonly connected to a control terminal of the first transistor, and a current according to the current passing through the first transistor in the main current path. A second transistor configured to flow through the third transistor; a third transistor whose main current path is connected in parallel to a resistor constituting the time constant circuit; and a third transistor receiving a current passing through the main current path of the second transistor. And a bias circuit for supplying a bias to the control terminal of the transistor. More preferably, a diode is provided in parallel with respect to the resistor constituting the time constant circuit.

A series regulator type voltage supply circuit is provided on the input side of the time constant circuit including a series circuit of a resistor and a capacitor. Here, inside the voltage supply circuit, a first transistor connected between the input terminal of the voltage supply circuit and the time constant circuit, a second transistor for performing a current mirror operation with the first transistor, and a resistance of the time constant circuit. A third transistor in which the main current paths are connected in parallel and a bias circuit for supplying a bias to the third transistor in accordance with a current supplied from the second transistor, specifically, a resistor are provided. More preferably, a diode is connected in parallel with the resistance of the time constant circuit.

When the supply of the voltage from the voltage supply circuit to the time constant circuit is started, the diode conducts when the voltage between the terminals of the capacitors of the time constant circuit is low. At this time, a current flowing through both the resistor and the diode flows into the capacitor, and the current passing through the first transistor becomes larger than when the resistor alone. As the current passing through the first transistor increases, the current passing through the second transistor also increases, and the third transistor turns on. The electrical resistance appearing in the main current path of the transistor element in the on state is very low, and the potential difference generated therein is lower than the forward drop voltage of the diode, so that the capacitor is rapidly charged.

When the charging of the capacitor proceeds and the voltage between the terminals rises, the third transistor cannot keep on. Specifically, when the voltage between the terminals of the capacitor rises to approximately the prescribed voltage value, the third transistor shifts to the off state. The third transistor then remains off as long as the voltage between the terminals of the capacitor maintains a high value. In this way, the third transistor is turned on and off substantially in accordance with the voltage between the terminals of the capacitor constituting the time constant circuit.

<Example>

1 shows a voltage supply circuit according to the present invention in which the capacitor of the time constant circuit can be quickly charged at the start of voltage supply. Here, the voltage supply circuit of FIG. 1 is composed of a voltage generation circuit 7a corresponding to the voltage generation circuit 7 of FIG. 2 and a time constant circuit 6 corresponding to the time constant circuit 6 of FIG. The voltage generating circuit 7a is configured as follows.

The main current path of the transistor Q1 is connected between the input terminal IN and the output terminal OUT, and the base of the transistor Q1 is connected to the ground through the main current path of the transistor Q4. The base of the transistor Q4 is connected to the signal output terminal of the error amplifier AMP, and the non-inverting input terminal + of the error amplifier AMP is connected to the bandgap reference circuit BG. The series circuit of the resistors R1 and R2 is connected between the output terminal OUT and the ground, and the common connection point of the resistors R1 and R2 is connected to the inverting input terminal (-) of the error amplifier AMP.

Transistor Q2 is provided in which transistors Q1, bases, and emitters are commonly connected, and a collector of transistors Q2 is connected to one end of resistor R3 as a bias circuit. The other end of the resistor R3 is connected to ground, and one end of the resistor R3 is connected to the base of the transistor Q3. The emitter is connected to one end of the resistor R0 and its collector to the other end of the resistor R0 so that the main current path of the transistor Q3 is in parallel connection with the resistor R0 in the time constant circuit 6. do. A transistor Q5 is formed between the collector and the base, and an emitter of the transistor Q5 is connected to one end of the resistor R0 and the collector is connected to the other end of the resistor R0.

The circuit of FIG. 1 having the above configuration performs the following operation.

First, when a voltage is supplied to the input terminal IN, the bandgap reference circuit BG and the error amplifier AMP are put into an operating state. By the way, the transistor Q1, the error amplifier AMP, the bandgap reference circuit BG, and the resistors R1 and R2 in the voltage generation circuit 7a have a circuit configuration of a series regulator. For this reason, the bandgap reference circuit BG in an operating state generates a BG voltage signal having a very high stability showing values around 1.26V at room temperature. The error amplifier AMP in an operating state drives the transistor Q1 so that the voltage at the common connection point of the resistors R1 and R2 is equal to the BG voltage signal supplied from the bandgap reference circuit BG.

When the capacitor C0 of the time constant circuit 6 is uncharged and the voltage between its terminals is low, the error amplifier AMP drives the transistor Q1 to increase the passage current of the transistor Q1. At this time, a large potential difference occurs between the terminals of the resistor R0 of the time constant circuit 6. Since the potential difference is larger than the on-voltage of the transistor Q5 operating as a diode, the transistor Q5 conducts and a large charging current is supplied to the capacitor C0 through the transistor Q5.

When a current flows in the transistor Q5, a larger current flows in the transistor Q1 than in the case of the resistor R0 alone, and accordingly, a larger current also flows in the transistor Q2 connected to form the current mirror circuit with the transistor Q1. Current flows The current passing through the transistor Q2 is supplied to one end of the resistor R3 and the base of the transistor Q3, so that the transistor Q3 is turned on. As the main current of the turned-on transistor Q3, the electrical resistance is very low, and the capacitor C0 is charged quickly.

When the charging of the capacitor C0 proceeds and the voltage between the terminals (i.e., the voltage V _R2 ) is close to the prescribed value, a series regulator is performed by a circuit portion consisting of Q1, Q4, AMP, BG, R1, and R2. As a result, the current passing through the transistor Q1 is narrowed. At this time, the passage current of the transistor Q2 is also narrowed at the same time, so that the potential rise of the emitter position of the transistor Q3 and the potential decrease of the position of the base proceed simultaneously. Then, the bias supplied to the transistor Q3 is lowered, and then the transistor Q3 transitions to the off state.

As described above, the transistor Q3 is turned on and off in accordance with the voltage between the terminals of the capacitor C0 and the current passing through the transistor Q1.

In the circuit of FIG. 1, when the transistor Q3 is turned on, the potential difference between the collector and the emitter is the forward drop voltage of the diode element, the collector, or the collector of the transistor Q5 shorted between the base, Lower than the potential difference between the emitters. For this reason, the capacitor C0 can be charged more quickly than the countermeasure which only connects a diode to the resistor R0 of the time constant circuit 6 (the specific example of the countermeasure of <1> mentioned above). The resistor R3 and transistor Q2 for supplying a bias to the transistor Q3 relate the resistance value and the size of the transistor (= magnitude of the passing current) to the resistance value and characteristics of the time constant circuit 6. Can be set without For this reason, it becomes easy to adjust the bias supply amount at the time of turn-on and turn-off of transistor Q3, and the bias supply amount at the time of holding on-state.

In addition, for the transistor Q5 serving as a diode, a larger current is passed through the transistor Q1 and the transistor Q2 by passing a larger current than when the resistor R0 alone is used to promote turn-on of the transistor Q3. It has a role to play. By setting the on-voltage of the transistor Q5 to an appropriate value, when the voltage between the terminals of the capacitor C0 is lower than the prescribed value due to an unforeseen situation, the transistor Q3 is turned on and the prescribed value is quickly set. The transistor Q3 can be prevented from being turned on incorrectly due to noise. However, the difference between the current flowing through the resistor R0 is very large at the time of starting (= voltage between terminals of capacitor C0 is zero) and normal operation (= voltage between terminals of capacitor C0 is specified value), If there is no need to promote turn-on of transistor Q3, transistor Q5 may be omitted.

When the voltage supply circuit of Fig. 1 is in the normal operation state, the circuit portion of the transistors Q1 and Q4, the error amplifier AMP, and the bandgap reference circuit BG in the voltage generation circuit 7a is constituted by the circuit. It can also be considered as a ripple filter in. When the voltage V _IN of the input terminal _IN of the voltage generating circuit 7a is sufficiently higher than the voltage V _OUT of the output terminal _OUT (= V _{R1 in} FIG. 2), the voltage generating circuit 7a By the ripple filter function, the noise included in the voltage V _IN is greatly reduced, and the voltage V _OUT becomes a DC voltage with less noise. Naturally, the voltage (voltage corresponding to V _R2 in FIG. 2) taken out from the time constant circuit 6 in FIG. 1 becomes a DC voltage with little noise.

On the other hand, when the voltage V _IN and the voltage V _OUT are approximated, the noise contained in the voltage V _IN passes through the voltage generating circuit 7a almost as it is. However, since the time constant circuit 6 functions as a low pass filter, as a result, the voltage taken out from the time constant circuit 6 of FIG. 1 (voltage corresponding to V _R2 of FIG. 2) becomes a DC voltage with low noise. . Therefore, even if the voltage generation circuit according to the present invention is applied to a conventional stabilization circuit, the circuit operation of the stabilization circuit itself is not impaired.

In the above description of the present invention, the transistor Q1, the error amplifier AMP, the bandgap reference circuit BG, and the resistors R1 and R2 in FIG. 1 constitute a series regulator. However, as long as there exists a transistor Q1 for adjusting the supply current to the time constant circuit 6, for example, a three-terminal regulator may be constituted. In addition, the voltage generation circuit 7a of the voltage supply circuit according to the present invention is not limited to the supply of the reference voltage of the voltage stabilization circuit as shown in FIG. 2, and supplies a high stability voltage through a time constant circuit (RC filter). It is widely applicable in the case.

Since both ends of the resistor constituting the time constant circuit are short-circuited by the third transistor which is turned on at the start of voltage supply, the resistance factor for current flow such as the forward drop voltage is small, so that the capacitor in the time constant circuit is quickly charged. can do.

Since the bias is supplied from the second transistor and the bias circuit which receives the current from the third transistor that shorts both ends of the resistor at the start of voltage supply, the bias is independent of the set value of the resistance of the time constant circuit. Quantity can be set. Then, it is turned on and off by adjusting the magnitude of the current passing through the second transistor, the bias supply amount from the bias circuit to the supply current, and the forward drop voltage (on voltage) of the diode connected in parallel with the resistor as necessary. And the bias amount to be supplied to the third transistor at each point in the on state maintenance can be easily adjusted.

Claims (6)

In a voltage supply circuit for supplying a voltage to a functional circuit installed on the output side of the time constant circuit through a time constant circuit comprising a resistor and a capacitor: A first transistor provided between an input terminal and the time constant circuit to supply a voltage and a current to the time constant circuit; A second transistor having a control terminal connected in common with a control terminal of the first transistor, the second transistor configured to flow a current corresponding to a current passing through the first transistor in a main current path thereof; A third transistor whose main current path is connected in parallel to a resistor constituting the time constant circuit; and And a bias circuit configured to receive a supply of current passing through a main current path of the second transistor and supply a bias to a control terminal of the third transistor. The third transistor of claim 1, wherein the bias circuit turns on the third transistor according to the magnitude of the current passing through the main current path of the first transistor when the voltage between the terminals of the capacitor constituting the time constant circuit is low. A voltage supply circuit comprising supplying a bias to be in a state. 3. The voltage supply circuit as claimed in claim 2, wherein said bias circuit is made of a resistance element. The apparatus according to any one of claims 1 to 3, wherein the feedback voltage signal equal to the voltage between the terminals of the time constant circuit and the reference voltage signal whose voltage value is stable are received, and according to the magnitudes of the two voltage signals. And an error amplifier for generating a signal for controlling a current through the first transistor, And the first transistor constitutes a regulator circuit for making the voltage between terminals of the time constant circuit constant with the error amplifier. The voltage supply circuit according to any one of claims 1 to 3, further comprising a diode connected in parallel with a resistor constituting the time constant circuit. The voltage supply circuit according to claim 4, further comprising a diode connected in parallel with a resistor constituting said time constant circuit.

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